Epoxy sizing composition for filament winding

ABSTRACT

A sizing composition containing an epoxy film former, a silane package that includes an aminosilane coupling agent and an epoxy silane coupling agent, a cationic lubricant, a non-ionic lubricant, an antistatic agent, and at least one acid is provided. The epoxy resin emulsion includes a low molecular weight liquid epoxy resin and one or more surfactants. The epoxy resin preferably has an epoxy equivalent weight of from about 185 to about 192. The sizing composition may optionally contain polyurethane or epoxy/polyurethane film former. The sizing composition may be used to size glass fibers used in filament winding applications to form reinforced composite articles with improved mechanical properties, wet tensile properties, improved resistance to cracking, and improved processing characteristics. The sizing composition also provides improved processing parameters such as low fuzz and reduced drag.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 10/872,103 entitled “Epoxy Sizing Composition For Filament Winding” filed Jun. 18, 2004, the entire content of which is expressly incorporated herein by reference.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention relates generally to size compositions for glass fibers, and more particularly, to size compositions containing an epoxy resin emulsion that includes a low epoxy equivalent weight epoxy resin for sizing glass fibers used in a filament winding application. A composite article formed from fibers sized with the sizing composition is also provided.

BACKGROUND OF THE INVENTION

Glass fibers are useful in a variety of technologies. For example, glass fibers are commonly used as reinforcements in polymer matrices to form glass fiber reinforced plastics or composites because they provide dimensional stability as they do not shrink or stretch in response to changing atmospheric conditions. In addition, glass fibers have high tensile strength, heat resistance, moisture resistance, and low thermal conductivity.

Typically, glass fibers are formed by attenuating streams of a molten glass material from a bushing or orifice. The molten glass may be attenuated by a winder which collects gathered filaments into a package or by rollers which pull the fibers before they are collected and chopped. An aqueous sizing composition is typically applied to the fibers after they are drawn from the bushing. Once the fibers are treated with the sizing composition, they may be dried in a package or chopped strand form. Drying the fibers evaporates the liquid medium and deposits the size as a residue lightly coating the surface of the glass fiber.

Conventional sizing compositions typically contain one or more film forming polymeric or resinous components, glass-resin coupling agents, and one or more lubricants dissolved or dispersed in a liquid medium. The film forming component of the size composition is desirably selected to be compatible with the matrix resin or resins in which the glass fibers are to be embedded. Epoxy resins and polyurethanes have been used as film forming components in size compositions. Epoxy resins are typically utilized where the fibers are to be used for reinforcing articles. Epoxy film formers are utilized in the sizing compositions of a wide variety of reinforcement systems for numerous resin systems. For example, glass fiber reinforced articles are prepared by impregnating continuous multifilament glass fiber strands with a curable resin composition, winding the glass fiber strands about a suitable form, and then curing the matrix resin. Specific examples of sizing compositions that contain epoxy resins are set forth below.

U.S. Pat. No. 4,104,434 to Johnson describes a sizing composition that contains a water emulsifiable resin system such as an epoxy resin, an aliphatic monocarboxylic acid, and an aliphatic polycarboxylic acid.

U.S. Pat. No. 4,107,118 to McCoy describes a glass sizing composition that contains an epoxy resin emulsion, a polyvinylpyrrolidone, and a polyethylene glycol ester monooleate. The patentee asserts that the sizing composition is particularly suitable for use in epoxy filament winding.

U.S. Pat. No. 4,140,833 to McCoy discloses a glass sizing composition that includes an epoxy resin emulsion, a polyvinylpyrrolidone, α-methacryloxypropyltriethoxysilane, and a polyethylene glycol ester monostearate. The patentee asserts that the sizing composition is particularly suitable for continuous pultrusion.

U.S. Pat. No. 4,305,742 to Barch et al. discloses a sizing composition for treating glass fibers that includes a phenolic epoxy resin, the reaction product of a partial ester of polycarboxylic acid that contains one or more unesterified carboxyl groups with a compound containing more than one epoxy group, a lubricant, emulsifiers or wetting agents, one or more silane coupling agents, and water.

U.S. Pat. No. 4,394,418 to Temple describes an aqueous sizing composition that includes a polyvinyl acetate silane copolymer, an epoxy polymer, one or more lubricants, an organosilane coupling agent, one or more non-ionic surfactants, a hydrocarbon acid, and water. The organosilane coupling agent may be an amino-organosilane coupling agent, a lubricant modified aminosilane coupling agent, an epoxy containing silane coupling agent, or a mixture of two or more of these coupling agents. Optionally, the sizing composition may also include a polyethylene-containing polymer, and/or a wax.

U.S. Pat. No. 4,448,910 to Haines et al. discloses an aqueous sizing composition for glass fibers that contains an emulsified epoxy resin, a lubricant, and 3-chloropropyltrimethoxysilane.

U.S. Pat. No. 4,448,911 to Haines et al. describes an aqueous sizing composition for glass fibers that has an emulsified epoxy resin as the film former, an emulsified mineral oil as the lubricant, glycidoxyalkyl and/or haloalkylsilanes as coupling agents, an amide antistatic agent, and polyvinlylpyrrolidone.

U.S. Pat. No. 4,656,084 to McCoy et al. discloses an aqueous sizing composition for glass fibers that contains epoxy- and methacrylyl-functional organosilanes, a fiber forming polymer such as an epoxy resin, a lubricant, and a pH regulator. McCoy et al. teach that the sizing composition is particularly suitable for glass fiber reinforcements for filament winding and pultrusion applications.

U.S. Pat. No. 4,933,381 to Hager discloses a size composition for sizing small diameter glass fibers. The sizing composition includes an epoxy film former resin, a non-ionic lubricant, a cationic lubricant, at least one organosilane coupling agent, at least one volatile or non-volatile acid, and water.

U.S. Pat. No. 5,038,555 to Wu et al. discloses a size composition that includes an epoxy as the film former, at least one emulsifying agent, at least one fiber lubricant, at least one organofunctional metallic coupling agent, polyvinylpyrrolidone, a water dispersible or emulsifiable polyethylene, and water.

U.S. Pat. No. 5,262,236 to Brannon describes an aqueous size composition for glass fibers that includes an epoxy resin, a coupling agent, and crystalline pentaerythritol. Brannon asserts that the sizing composition is particularly suitable for glass fiber reinforcements for filament winding and pultrusion applications.

U.S. Pat. No. 6,270,897 to Flautt et al. discloses a sizing composition that contains a combination of at least one diol organosilane and at least one triol organosilane. The sizing composition may also contain film-forming polymeric materials such as epoxy resins and lubricants.

The sizing composition is applied to the fibers to reduce interfilament abrasion and breakage during subsequent processing and to improve the compatibility of the fibers with the matrix resin that is to be reinforced. In addition to improving the processability of the fiber and the fiber-polymer coupling, the sizing composition should also enhance the physical properties of the composite article formed from the reinforced fiber. Accordingly, in view of the dual role of the sizing compositions in improving the processability of the fibers while improving the physical properties of the resulting composite and the wide variety of polymeric materials that can be reinforced with glass fibers, a continuing need exists in the art for specifically tailored sizing compositions that provide enhanced physical properties and processing characteristics to reinforced composite articles.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a sizing composition for glass fibers that includes an epoxy resin emulsion, a silane package including at least one aminosilane coupling agent and at least one epoxy silane coupling agent, a non-ionic lubricant, a cationic lubricant, an antistatic agent, an organic acid, and a boron-containing compound. The epoxy resin emulsion contains an epoxy resin and at least one surfactant. It is preferred that the epoxy resin have an epoxy equivalent weight of from about 180 to about 210, and even more preferably from about 180 to about 195. Although the size composition may be applied to any glass fiber, the performance of the size is optimized when low-to-no boron-containing glass fibers are utilized. Examples of suitable organic acids that may be used in the size composition include acetic acid, formic acid, succinic acid, and/or citric acid. Acetic acid is the most preferred organic acid for use in the size composition. Boric acid is the most preferred boron-containing compound. The size composition reduces drag and the amount of fuzz generated by the glass fibers passing through contact points during subsequent processing. In addition, the reduction in drag reduces the amount of size that is deposited onto the contact points from the glass fibers during processing. The sizing composition is advantageously employed to coat fibers used in filament winding applications.

It is another object of the present invention to provide a composite article that is formed of a plurality of glass fibers sized with a sizing composition that includes an epoxy resin emulsion, a silane package that includes at least one aminosilane coupling agent and at least one epoxy silane coupling agent, a non-ionic lubricant, a cationic lubricant, an antistatic agent, an organic acid, and a boron-containing compound. The reinforced composite product made from fibers sized with the sizing composition demonstrate improved physical properties such as improved wet mechanical properties, improved strength, and superior processing characteristics such as faster impregnation of a glass strand by the epoxy resin, a low level of broken filaments, and a smoother surface of the pipe.

It is an advantage of the sizing composition that the low molecular weight epoxy resin emulsions present in the size composition are in a liquid form that reduces or eliminates the need for an organic solvent in the sizing composition. The reduction of organic solvents in the size in turn reduces the amount of volatile organic compounds that are emitted, thereby creating a safer, more environmentally friendly workplace.

It is also an advantage of the present invention that the film forming emulsions are substantially color free and disperse easily in water.

It is another advantage of the sizing composition that composite articles formed from fibers sized with the sizing composition demonstrate improved wet tensile strength performance, improved cyclic and static fatigue, and improved resistance to cracking. Improved pipe cyclic and static fatigue may permit a pipe manufacturer to reduce the thickness of the pipe wall in a composite part sized with the inventive sizing composition and achieve an improved level of leak resistance in the pipe. In addition, a thinner pipe wall results in a reduction in the pipe's overall weight and a reduction in materials used to form the pipe, thereby reducing manufacturing costs.

It is also an advantage of the present invention that the small amount of boron present in the size composition reduces the amount of boron present in the air and assists in making the inventive size composition environmentally friendly.

It is a further advantage of the present invention that the size composition reduces or eliminates package growth and reduces the number of deformed packages.

It is another advantage of the present invention that the size composition provides superior processing characteristics such as faster impregnation of a glass strand by the epoxy resin, a low level of broken filaments (fuzz), and a reduction in drag.

It is yet another advantage of the present invention that the size composition reduces the occurrence of migration in the final package. Thus, the amount of the external portion of the package that would be removed as waste as a result of size migration is reduced or eliminated by utilizing the inventive sizing composition.

It is also an advantage of the present invention that the size composition reduces the friction generated between the contact points and the sized glass fibers (drag) in the manufacturing process and thus reduces the level of fuzz on the glass fibers.

The foregoing and other objects, features, and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description that follows.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. All references cited herein, including published or corresponding U.S. or foreign patent applications, issued U.S. or foreign patents, or any other references, are each incorporated by reference in their entireties, including all data, tables, figures, and text presented in the cited references. It is to be noted that the phrases “size composition”, “sizing composition”, “size”, and “sizing” are used interchangeably herein.

The present invention relates to improved sizing compositions for fibers that may be advantageously used in filament winding processes. The sizing composition includes an epoxy film former, a silane package that includes an aminosilane coupling agent and an epoxy silane coupling agent, a cationic lubricant, a non-ionic lubricant, an antistatic agent, and at least one acid. In addition, the sizing composition may also contain a polyurethane or epoxy/polyurethane film former.

The epoxy film forming polymer component of the sizing composition includes epoxy resin emulsions that contain a low molecular weight epoxy resin and at least one surfactant. The film former functions to protect the fibers from damage during processing and imparts compatibility of the fibers with the matrix resin. It is preferred that the epoxy resin have a molecular weight of from about 360 to about 420 and an epoxy equivalent weight of from about 180 to about 210, more preferably a molecular weight from about 360 to about 390 and an epoxy equivalent weight of from about 180 to about 195, and most preferably a molecular weight of from about 370 to about 384 and an epoxy equivalent weight of from about 185 to about 192. “Epoxy equivalent weight”, as used herein, is defined by the molecular weight of the epoxy resin divided by the number of epoxy groups present in the compound. Useful epoxy resins contain at least one epoxy or oxirane group in the molecule, such as polyglycidyl ethers of polyhydric alcohols or thiols. Examples of suitable epoxy film forming resins include Epon® 828 (available from Hexion Specialties Chemicals Incorporated), DER 331 (available from Dow Chemicals), Araldite 6010 (available from Huntsman), and Epotuf 37-140 (available from Reichhold Chemical Co).

The low molecular weight epoxy resin emulsions are preferably in a liquid form which reduces, and in some cases, eliminates the need for a solvent such as diacetone alcohol. This reduction of organic solvents in turn reduces the amount of VOC's (volatile organic compounds) that are emitted into the environment. In addition, the low molecular weight epoxy film forming emulsions according to the present invention are substantially color free. As used herein, the term “substantially color free” means that there is minimal or no coloration of the epoxy emulsions. Another advantage of the inventive epoxy emulsions is that they disperse easily in water. The inventive epoxy resins also provide for better wetting of the resin, a greater epoxy reactivity, improved coating quality, improved emulsion dispersion, and reduced strand stiffness.

Examples of suitable surfactants for use in the epoxy resin emulsion include, but are not limited to, Triton X-100, an octylphenoxypolyethoxyethanol (available from Union Carbide Corp.), Pluronic P103, an ethylene oxide/propylene oxide block copolymer (available from BASF), Pluronic F77, an ethylene oxide/propylene oxide block copolymer (available from BASF), Pluronic 10R5, an ethylene oxide/propylene oxide block copolymer (available from BASF), a block copolymer of ethylene oxide and propylene oxide such as Pluronic L101 (available from BASF), a polyoxyethylene-polyoxypropylene block copolymer such as Pluronic P105 (available from BASF), and an ethylene oxide/propylene oxide copolymer (available from BASF). Preferably, the epoxy resin emulsion contains two or more surfactants. In a preferred embodiment, a combination of (1) a block copolymer of ethylene oxide and propylene oxide and (2) a polyoxyethylene-polyoxypropylene block copolymer (such as Pluronic L101 and Pluronic P105) is used in the epoxy resin emulsion. The surfactant or surfactants may be present in the epoxy resin emulsion in an amount of from about 10 to about 25%, and most preferably in an amount of about 18%.

The epoxy resin emulsion is present in the size composition in an amount of from about 60 to about 90% by weight solids and preferably from about 70 to about 80% by weight solids.

A comparison of a conventional epoxy resin emulsion and an inventive film forming epoxy resin emulsion is set forth in Table 1. TABLE 1 Physical Epoxy Film State of Film Base Equivalent Pluronic Former Epoxy Solvent Former Status Epoxy Weight surfactant Solids resin Present AD-502 Conventional DER 337 230-250 18% 64% Semi-solid Yes RSW-3952 Inventive Epon ® 185-192 18% 61% Liquid No 828

The silane package utilized in the size composition includes an at least one aminosilane coupling agent and at least one epoxy silane coupling agent. The coupling agents used in the silane package of the size composition may have hydrolyzable groups that can react with the glass surface to remove unwanted hydroxyl groups and one or more groups that can react with the film-forming polymer to chemically link the polymer with the glass surface. In particular, the coupling agents preferably include 1-3 hydrolyzable functional groups that can interact with the surface of the glass fibers and one or more organic groups that are compatible with the polymer matrix.

Suitable coupling agents for use in the silane package have a readily hydrolyzable bond to a silicon atom of the silane, or hydrolysis products thereof. Silane coupling agents which may be used in the present size composition may be characterized by the functional groups amino, epoxy, azido, vinyl, methacryloxy, ureido, and isocyanato. In addition, the coupling agents may include an acryl or methacryl group linked through non-hydrolyzable bonds to a silicon atom of the silane.

Coupling agents for use in the silane package include monosilanes containing the structure R′Si(OR)₃, where R is an organic group such as an alkyl group. Lower alkyl groups such as methyl, ethyl, and isopropyl are preferred. Silane coupling agents function to enhance the adhesion of the film forming agent to the glass fibers and to reduce the level of fuzz, or broken fiber filaments, during subsequent processing. Examples of suitable aminosilane coupling agents for use in the silane package include, but are not limited to aminopropyltriethoxysilane (A-1100 from GE Silicones), N-β-aminoethyl-γ-aminopropyltrimethoxysilane (A-1120 from GE Silicones), N-phenyl-γ-aminopropyltrimethoxysilane (Y-9669 from GE Silicones), and bis-γ-trimethoxysilylpropylamine (A-1170 from GE Silicones). Preferably, the aminosilane coupling agent is aminopropyltriethoxysilane (A-1100 from GE Silicones). The amino silane coupling agent may be present in the size composition in an amount of from about 0.4 to about 0.8% by weight solids, preferably in an amount of from about 0.4 to about 0.6% by weight solids. Although not wishing to be bound by theory, it is believed that the presence of a minimal amount of aminosilane coupling agent in the inventive sizing composition improves the mechanical properties of the final product. Too much aminosilane coupling agent added to the sizing composition may deteriorate mechanical properties.

Non-limiting examples of suitable epoxy silane coupling agents include a glycidoxy polymethylenetrialkoxysilane such as 3-glycidoxy-1-propyl-trimethoxysilane, an acryloxy or methacrylyloxypolymethylenetrialkoysilane such as 3-methacrylyloxy-1-propyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane (A-187 available from GE Silicones), γ-methacryloxypropyltrimethoxysilane (A-174 available from GE Silicones), α-chloropropyltrimethoxysilane (KBM-703 available from Shin-Etsu Chemical Co., Ltd.), α-glycidoxypropylmethyldiethoxysilane (A-2287 available from GE Silicones), and vinyl-tris-(2-methoxyethoxy)silane (A-172 from available GE Silicones). In at least one preferred embodiment, the epoxy silane coupling agent is γ-glycidoxypropyltrimethoxysilane (A-187) described above. The epoxy silane coupling agent may be present in the size composition in an amount of from about 10 to about 20% by weight solids, preferably from about 10 to about 16% by weight solids, and even more preferably from about 10 to about 14% by weight solids.

Additionally, the sizing composition contains at least one non-ionic lubricant. The non-ionic lubricant in the sizing composition acts as a “wet lubricant” and provides additional protection to the fibers during the filament winding process. In addition, the non-ionic lubricant helps to reduce the occurrence of fuzz. Especially suitable examples of non-ionic lubricants include PEG 200 Monolaurate (a polyethylene glycol fatty acid ester commercially available from Cognis) and PEG 600 Monooleate (Cognis). Other non-limiting examples include a polyalkylene glycol fatty acid such as PEG 600 Monostearate (a polyethylene glycol monostearate available from Cognis), PEG 400 Monostearate (Cognis), PEG 400 Monooleate (Cognis), and PEG 600 Monolaurate (Cognis). In a most preferred embodiment, the non-ionic lubricant is PEG 200 Monolaurate. The non-ionic lubricant may be present in the size composition in an amount from approximately about 6 to about 10% by weight solids, preferably from about 7 to about 9% by weight solids.

In addition to the non-ionic lubricant, the sizing composition also contains at least one cationic lubricant and at least one antistatic agent. The cationic lubricant aids in the reduction of interfilament abrasion. Suitable examples of cationic lubricants include, but are not limited to, a polyethyleneimine polyamide salt commercially available from Cognis under the trade name Emery 6760L, a stearic ethanolamide such as Lubesize K-12 (AOC), Cirrasol 185AE (Unichemie), and Cirrasol 185AN (Unichemie). The amount of cationic lubricant present in the size composition is preferably an amount sufficient to provide a level of the active lubricant that will form a coating with low fuzz development. In at least one exemplary embodiment, the cationic lubricant is present in the size composition in an amount of from about 0.01 to about 1.0% by weight solids, preferably from about 0.03 to about 0.06% by weight solids.

Antistatic agents especially suitable for use herein include antistatic agents that are soluble in the sizing composition. Examples of suitable antistatic agents include compounds such as Emerstat™ 6660A and Emerstat™ 6665 (quaternary ammonium antistatic agents available from Emery Industries, Inc.), and Larostat 264A (a quaternary ammonium antistatic agent available from BASF), tetraethylammonium chloride, and lithium chloride. Antistatic agents may be present in the size composition in an amount of from about 0.4 to about 0.8% by weight solids, preferably from about 0.4 to about 0.6% by weight solids.

The total amount of the cationic lubricant and the antistatic agent that is present in the size composition may range from about 0.4 to about 0.8% by weight solids, preferably from about 0.4 to about 0.7% by weight solids. It is preferred, however, that the amount of cationic lubricant and antistatic agent present in the size composition is an amount that is less than or equal to about 1.0% by weight solids.

Further, the sizing composition may contain a small amount of at least one weak organic acid. Although not wishing to be bound by theory, it is believed that citric acid, a conventional acid additive for sizing compositions used to adjust the pH, may prematurely open the epoxy groups in the film formers and epoxy silanes if used in large amounts during the drying of the glass fibers, which may result in a reduction of mechanical properties. In the inventive size composition, a trace amount of acetic acid, formic acid, succinic acid, and/or citric acid may be added to the inventive sizing composition to hydrolyze the silane in the coupling agent without prematurely opening the epoxy groups. It is preferred that the organic acid is acetic acid. In especially preferred embodiments, the organic acid (such as acetic acid) is present in the size composition in an amount of from about 0.4 to about 1.0% by weight solids, preferably from about 0.5 to about 0.7% by weight solids.

In addition, the size composition contains a boron-containing compound that is capable of providing boron atoms to the size composition. It is hypothesized that the boron atoms released from the boron-containing compound act with the aminosilane at the glass interface to assist in adhering the remaining sizing components to the glass fiber. In addition, it has been discovered that the combination of a boron containing compound such as boric acid in the size composition, together with an aminosilane (e.g., A-1100), and an epoxy silane (e.g., A-187), improves the mechanical properties of the final product. Non-limiting examples of suitable boron-containing compounds include boric acid and borate salts such as boron oxide, sodium tetraborate, potassium metaborate, potassium tetraborate, ammonium biborate, ammonium tetrafluoroborate, butylammonium tetrafluoroborate, calcium tetrafluoroborate, lithium fluoroborate, potassium tetrafluoroborate, sodium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, and zinc tetrafluoroborate. Preferably, the boron-containing compound is boric acid. The boron-containing compound is present in the sizing composition in an amount of from about 0.2 to about 3.0% by weight solids, preferably from about 0.2 to about 1.0% by weight solids, and most preferably from about 0.2 to about 0.6% by weight solids.

The combination of the organic acid (e.g., acetic acid) and boric acid in the size composition desirably imparts a pH of from about 3.0 to about 7.0, and more preferably a pH of from about 3.5 to about 5.5 to the size composition.

Optionally, the size composition may contain a polyurethane film former such as Baybond 2297 (Bayer), Baybond PU403 (Bayer), and W-290H (Chemtura) or an epoxy/polyurethane film former such as Epi-Rez 5520-W-60 (Hexion Specialties Chemicals Incorporated). It is believed that the polyurethane film former increases strand integrity and mechanical fatigue performance by toughening the resin/size interphase. The toughened resin interphase may result in a final composite product that has an improved resistance to cracking and has increased or improved mechanical properties such as improved strength. The polyurethane film former may be present in the sizing composition an amount of from about 0 to about 10% by weight solids, preferably in an amount of from about 0 to about 5% by weight solids.

The size composition further includes water to dissolve or disperse the active solids for coating. Water may be added in an amount sufficient to dilute the aqueous sizing composition to a viscosity that is suitable for its application to glass fibers and to achieve the desired solids content on the fibers. The mix solids content of the size may be from about 1.0 to about 15%, preferably from about 5 to about 10%, and most preferably from about 8.0 to about 8.5%. In preferred embodiments, the sizing composition may contain up to about 92% water.

The range of components utilized in the sizing composition is set forth in Table 2. TABLE 2 Sizing Component % by Weight Solids Epoxy Resin Emulsion about 60 to about 90 Aminosilane Coupling about 0.4 to about- 0.8 Agent Epoxy Silane Coupling about 10 to about 20 Agent Non-Ionic Lubricant about 6 to about 10 Cationic about 0.4 to about 0.8 Lubricant/Antistatic Agent Acetic Acid about 0.4 to about 1.0 Boric Acid about 0.2 to about 3.0 Polyurethane or about 0 to about 10 Epoxy/Polyurethane Film Former

A preferred aqueous sizing composition according to the present invention is set forth in Table 3. TABLE 3 Sizing Component % by Weight Solids Epoxy Resin Emulsion about 70 to about 80 Aminosilane Coupling Agent about 0.4 to about 0.6 Epoxy Silane Coupling Agent about 10 to about 14 Non-Ionic Lubricant about 7 to about 9 Cationic Lubricant/Antistatic Agent about 0.4 to about 0.7 Acetic Acid about 0.5 to about 0.7 Boric Acid about 0.2 to about 1.0 Polyurethane Film Former about 0 to about 5

The size composition may be made by adding water, acetic acid, and an aminosilane coupling agent to a main mix container with agitation. The pH is adjusted with additional acetic acid to a pH of less than about 5.5 if necessary. Once a pH of less than about 5.5 is achieved, an epoxy silane coupling agent is added to the main mix container and the mixture is agitated to hydrolyze the silane coupling agents. Once the silane hydrolysis is complete, a pre-mix containing the epoxy resin emulsion, the non-ionic lubricant, and water is added to the main mix container. The cationic lubricant, the antistatic agent, and the boric acid are then separately added with agitation. If necessary, the main mixture is adjusted to a final pH level of about 3.0 to about 7.0.

The size composition may be applied to strands of glass formed by conventional techniques such as by drawing molten glass through a heated bushing to form substantially continuous glass fibers. Any type of glass, such as A-type glass, C-type glass, E-type glass, S-type glass, R-type glass, AR-type glass, E-CR-type glass (commercially available from Owens Corning Fiberglass Corporation under the trade name Advantex®), or modifications thereof may be used. Although any glass fiber may be utilized, the size performance is optimized when Advantex® glass fibers are used. The size composition may be applied to fibers having a diameter of from about 4 to about 30 microns, with fibers of from about 12 to about 23 microns in diameter being more preferred. In addition, the size composition may be applied to single or multi-filament fiber strands. Each strand may contain from about 2000 to about 4000 fibers.

The sizing composition may be applied to the fibers in any conventional manner using any conventional application technique such as by spraying or drawing the fibers to be sized across a rotating or stationary roll that is wetted with the sizing composition. It is desirable to have as low a moisture content in the size composition as possible to reduce the migration of the size to the outside of the final dry package. The size composition may be applied to the fibers in an amount sufficient to provide the fibers and the final wet package with a moisture content of from about 3% by weight to about 15% by weight. However, it is preferred that the size composition is applied such that that percent forming moisture of the final wet package has a moisture content of from about 5 to about 10% by weight, preferably from about 5 to about 8% by weight, and most preferably from about 5 to about 6% by weight. By reducing the amount of water in the size composition and therefore in the final wet package, migration that may occur in the final package is reduced or eliminated. Thus, the amount of the external portion of the package that would have to be removed as waste as a result of size migration is reduced or eliminated by utilizing the inventive sizing composition.

The size composition is preferably applied to the glass fibers and dried such that the size is present on the fibers in an amount of from about 0.3 to about 1.25 percent by weight based on the total weight of the fibers. This can be determined by the loss on ignition (LOI) of the fiber, which is the reduction in weight experienced by the fibers after heating them to a temperature sufficient to burn or pyrolyze the organic size from the fibers.

The sizing composition is advantageously employed to coat the fibers used in a filament winding application. For example, the fibers may be coated or treated with the sizing composition and formed into a roving in a conventional manner. The sized roving may then be wound onto a mandrel. The mandrel may be any conventional mandrel such as a reusable mandrel, a collapsible mandrel, an integral mandrel, or a sacrificial mandrel. Once the roving has been wound about the mandrel, the composite part and mandrel are heated, such as by passing the composite part/mandrel through an oven or by passing hot air or steam through the mandrel. Once the composite is cured and cooled, the mandrel may be removed. Composite parts such as pipes or tanks made from fibers sized with the size composition of the present invention demonstrate superior strength and superior processing characteristics such as faster impregnation of the strand with the epoxy resin, a reduced amount of broken filaments, and a smoother surface of the pipe.

One advantage of the inventive size composition is the ability of the size composition to reduce drag. A reduction in drag in the sized glass fibers permits the manufacturers to run their production lines at a faster rate than with a glass fiber that has a high drag. As a result, an increase in the productivity may be achieved with the inventive sizing composition. The reduction in drag in turn causes a reduction in fuzz, or broken fibers, that occurs as the final products are being made. The occurrence of fuzz may cause some manufacturing downtime and may result in a product with a rough surface which is not aesthetically pleasing. In addition, the reduction in drag reduces the amount of the sizing composition that is deposited onto the contact points from the glass fibers during processing. Fuzz is also undesirable because the broken fibers on the surface of the glass may irritate the skin to those individuals in close contact with it.

The inventive sizing composition also provides package stability. Conventionally, when a package enters a drying oven, the package has a height of about 10½ inches. However, when it exits the drying oven, the package may expand in height and/or width, such as to a height of approximately 11½ inches. Package growth is undesirable because these expanded packages may not fit onto customers' creels for further processing of the glass strands. As a result, the expanded packages are often discarded as waste. The inventive size composition reduces, and in some cases, eliminates package growth so that the dried package remains within customer specifications. In addition, the size composition of the present invention provides for a reduction in the number of deformed packages that emerge from the drying oven.

A further advantage of the sizing composition according to the present invention is the ability of the sized glass fibers to be unwound from the package with little or no force. The inventive size composition provides enough stability to the package so that the package will run out completely without the package collapsing (shelling).

Having generally described this invention, a further understanding can be obtained by reference to certain specific examples illustrated below which are provided for purposes of illustration only and are not intended to be all inclusive or limiting unless otherwise specified.

EXAMPLES Example 1 Testing for the Occurrence of Fuzz on Sized Glass Fibers

The size composition set forth in Table 4 was prepared and applied to glass fibers having diameters of 17-23 microns by conventional techniques. The size composition was applied to the fibers in an amount sufficient to achieve a Loss on Ignition (LOI) of 0.45-0.77%. The sized fibers were then dried in a conventional manner at a temperature and for a time sufficient to both dry and cure the sizing on the glass fibers. TABLE 4 Size Composition A % by Sizing Weight Component Solids Epoxy Resin Emulsion 75.6 Aminosilane Coupling 0.6 Agent Epoxy Silane Coupling 13.7 Agent Non-Ionic Lubricant 8.0 Cationic 0.65 Lubricant/Antistatic Agent Acetic Acid 0.7 Boric Acid 0.6

The glass fibers sized with Size Composition A set forth in Table 4 were then tested in a bench scaled test to determine amount of fuzz generated by the glass fibers. The testing was conducted by running the glass fibers over a set of 11 separate contact points at a rate of 400 feet per minute until approximately two pounds of glass fibers were collected onto a wheel. Any “fuzz” (broken filaments) that occurred during the testing was collected by a vacuum system positioned below the glass fiber line at a location after the 11^(th) contact point. The “fuzz” was collected during the running of the test. The amount of fuzz collected by the vacuum system was weighed (mg) and divided by the weight of the glass fibers actually collected on the wheel (kg) to determine the amount (i.e., mg/kg) of fuzz generated by the fibers passing through the contact points.

Glass fibers sized with Control 1, which is the closest current epoxy compatible product for filament winding from Owens Corning and is a sizing formed in accordance with the description set forth in co-pending parent application U.S. patent application Ser. No. 10/872,103 entitled “Epoxy Sizing Composition For Filament Winding” filed Jun. 18, 2004 (expressly incorporated by reference in its entirety), and Controls 2 and 3, which are current epoxy compatible products for filament winding that are commercially available from Owens Corning, were tested in the same manner described above and compared to the glass fibers sized with Size Composition A. The control products used sizing chemistries for epoxy filament winding that included silane coupling agents, epoxy film formers, and various lubricants.

The results of the experiments are set forth in Table 5. TABLE 5 Fuzz Sample (mg/kg) Inventive Size A 9 Control 1 72 Control 2 73 Control 3 156.3

As shown in Table 5, glass fibers sized with inventive Size Composition A demonstrated the lowest occurrence of fuzz generated by the glass fibers by passing through the contact points. This significant reduction in the amount of fuzz produced by glass fibers sized with inventive Size Composition A demonstrates an improvement in processability for inventive Size Composition A over the each of the controls. Fuzz is an undesirable feature in the manufacturing of parts, and thus the ability of a glass fiber to demonstrate low fuzz occurrence has a clear market advantage. The low fuzz generated by fibers sized with Size Composition A permits manufacturers of final products to be able to run their production line at a fast rate with little to no breakage in the fibers. In addition, the reduction in fuzz on the glass fibers sized with Size Composition A will result in a product that has a smoother surface and that is aesthetically pleasing. Further, less maintenance of the production lines may occur with a reduction in the occurrence of fuzz because the contact points would need to be cleaned less frequently.

Example 2 Testing for Drag of Sized Glass Fibers

Glass fibers sized with inventive Size Composition A set forth in Table 4 were tested to determine amount of drag (frictional resistance) generated by the glass fibers. The testing was conducted by running the glass fibers over 11 contact points at a rate of 400 feet per minute. A tension meter was positioned at a location after the 11^(th) contact point to measure the tension of the glass fibers. Tension was measured over a time period of 15 seconds. Three measurements were taken and averaged to achieve the data set forth in Table 6.

Glass fibers sized with Control 1, which is the closest current epoxy compatible product for filament winding from Owens Corning and is a sizing formed in accordance with the description set forth in co-pending parent application U.S. patent application Ser. No. 10/872,103 entitled “Epoxy Sizing Composition For Filament Winding” filed Jun. 18, 2004 (expressly incorporated by reference in its entirety), and Controls 2 and 3, which are current epoxy compatible products for filament winding that are commercially available from Owens Corning, were tested in the same manner described above and compared to the glass fibers sized with Size Composition A. The control products used sizing chemistries for epoxy filament winding that included silane coupling agents, epoxy film formers, and various lubricants. TABLE 6 Drag (Kg/end Sample of fiber Inventive Size A 1.66 Control 1 2.26 Control 2 2.66 Control 3 2.63

The data set forth in Table 6 demonstrates the low dynamic tension (low frictional resistance or drag) that occurs in the glass fibers sized with inventive Size Composition A. As shown in Table 6, the glass fibers sized with Size Composition A had significantly lower drag values than any of the comparative sized glass fibers. This significant reduction in drag in glass fibers sized with inventive Size Composition A demonstrates an improvement in the processability of inventive Size Composition A over the each of the controls. Low drag is a desired property in sized glass fibers. A reduction in drag such as is caused by inventive Size Composition A permits manufacturers to run their production lines at a faster rate than with a glass fiber that has a high drag and increase their productivity.

Example 3 Effect on Pipe Axial Tensile Strength, 7 Day Boil

Glass fibers sized with Size Composition A (shown in Table 4) were helically wound about a mandrel and cured to form amine cured epoxy pipes. Pipes were also made using Control 1, which is the closest current epoxy compatible product for filament winding from Owens Corning and is a sizing formed in accordance with the description set forth in co-pending parent application U.S. patent application Ser. No. 10/872,103 entitled “Epoxy Sizing Composition For Filament Winding” filed Jun. 18, 2004 (expressly incorporated by reference in its entirety), and Control 2, which a current epoxy compatible product for filament winding that is commercially available from Owens Corning. The control products used sizing chemistries for epoxy filament winding that included silane coupling agents, epoxy film formers, and various lubricants.

The pipes made and used in this experiment were 12 foot long pipes that had an inside diameter of 2.235 inches and a wall thickness of about 0.060 inches. The pipes were made on a Mclean-Anderson filament winding machine using a filament winding process in which glass rovings sized with the appropriate sizing compositions were dipped into a resin bath, excess resin was removed by squeegees, and the wetted roving was wound onto the pipe at a 54.75 degree angle. The completed (wound) pipe and mandrel were transferred to a pipe curing oven to chemically crosslink the epoxy matrix to form the finished pipe. After cooling, the pipe was removed from the mandrel and cut into four sections. Some of the pipe was cut into longitudinal sections for axial tensile strength measurements and other sections of the pipe were used for pipe cyclic fatigue testing.

The portions of the pipe used for axial tensile strength measurements were cut longitudinally into test strips 0.5 in wide and 10 inches long. The strips were tested for axial tensile strength according to the method disclosed in ASTM D2105 except that the longitudinal test strips were tested instead of a whole pipe. The samples were broken using an Instron testing machine. Some of the samples were tested dry and other samples were immersed in boiling water for 7 days and then tested. The results are shown in Table 7. TABLE 7 Axial Tensile, 7 day boil Sample (ksi) Inventive Size A 6.76 Control 1 6.99 Control 2 5.51

The data in Table 7 shows that Size Composition A demonstrated outstanding wet strength properties and was comparable in strength to Control 1. The ability of a sizing composition to resist water degradation is a desired property if the composite pipe is to have long term performance. Long term performance of composite pipe under high temperature and pressure under wet conditions is measured by pipe manufacturers. It is believed that very high wet strength performance may be related to better long term performance. The results set forth in Table 7 illustrates that the pipe formed from Size Composition A had the same or improved wet mechanical properties over the current state of the art.

Example 4 Effect of Pipe Cyclic Fatigue

Glass fibers sized with Size Composition A (shown in Table 4) and Controls 1 and 2 were tested for pipe cyclic fatigue in both an amine cured and an anhydride cured epoxy pipe. The test was conducted according to ASTM D2992, part A. The test was conducted three times in the amine cured epoxy pipe and once in the anhydride cured epoxy pipe. The pipes were made in the same manner as described above in Example 3. A detailed description of the experimental procedure is set forth below.

In this example, a section of pipe approximately 30 inches long was installed with end fittings that had a port to accept water under high pressure. The pipe was filled with water and subjected to a cyclic test where the interior of the pipe was pressurized then depressurized. The cycle testing rate was about 25 cycles per minute. As the test progressed, cracks appeared in the pipe due to the applied pressure. These cracks are typically one of three types: resin matrix cracking, cracking due to de-bonding between the glass matrix interface, and de-bonding between layers of helically wound glass and resin. Over time, water penetrated the cracks in the pipe to the surface of the pipe. The penetration of the water through the pipe wall was termed a leak or a pipe failure. Leaks were electronically detected by completing an electrical circuit that was set up by wrapping the pipe with a conductive metal foil. When a leak was detected, the counter was stopped and the number of cycles were recorded. The pipe was then taken apart and the wall thickness of the pipe was measured.

The data obtained from the cyclic testing was plotted and fitted to a line using linear regression. The logarithm of the hoop stress was plotted against the logarithm of the cycles. The samples were then compared by selecting a hoop stress and determining the corresponding number of cycles. The higher the number of cycles conducted, the higher the performance. The results are shown in Table 8. TABLE 8 Cycles at 21,880 (psi) Sample stress Inventive Size A 1230 Control 1 1072 Control 2 528

Table 8 shows that pipes made with glass fibers sized with Size Composition A had outstanding pipe cyclic fatigue. Improving pipe cyclic fatigue can allow a pipe manufacturer to reduce the thickness of the pipe wall and maintain the same level of leak resistance. The thinner wall may result in a reduction in the pipe's overall weight and a reduction in materials used to form the pipe, which may result in a reduction in manufacturing costs.

The invention of this application has been described above both generically and with regard to specific embodiments. Although the invention has been set forth in what is believed to be the preferred embodiments, a wide variety of alternatives known to those of skill in the art can be selected within the generic disclosure. The invention is not otherwise limited, except for the recitation of the claims set forth below. 

1. An aqueous sizing composition comprising: an epoxy resin emulsion containing a liquid epoxy resin having an epoxy equivalent weight of from about 180 to about 210 and at least one surfactant; a silane package including at least one aminosilane coupling agent and at least one epoxy silane coupling agent; a cationic lubricant; a non-ionic lubricant; an antistatic agent; at least one organic acid; and a boron-containing compound.
 2. The aqueous sizing composition of claim 1, wherein said epoxy equivalent weight is about 185 to about
 192. 3. The aqueous sizing composition of claim 1, wherein said at least one organic acid is selected from at least one of acetic acid, formic acid, succinic acid and citric acid.
 4. The aqueous sizing composition of claim 3, wherein said boron-containing compound is selected from at least one of boric acid, boron oxide, sodium tetraborate, potassium metaborate, potassium tetraborate, ammonium biborate, ammonium tetrafluoroborate, butylammonium tetrafluoroborate, calcium tetrafluoroborate, lithium fluoroborate, potassium tetrafluoroborate, sodium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate and zinc tetrafluoroborate.
 5. The aqueous sizing composition of claim 1, further comprising at least one member selected from at least one of a polyurethane film former and an epoxy/polyurethane film former.
 6. The aqueous sizing composition of claim 1, wherein said epoxy resin emulsion is present in said sizing composition in an amount of from about 60 to about 90% by weight solids, said aminosilane coupling agent is present in said sizing composition in an amount of from about 0.4 to about 0.8% by weight solids, said epoxy silane coupling agent is present in said sizing composition in an amount of from about 10 about 20% by weight solids, said non-ionic lubricant is present in said sizing composition in an amount of from about 6 to about 10% by weight solids, said cationic lubricant and antistatic agent are present in said sizing composition in an amount of from about 0.4 to about 0.8% by weight solids, said at least one organic acid is present in said sizing composition in an amount of from about 0.4 to about 1.0% by weight solids and said boron-containing compound is present in said sizing composition in an amount of from about 0.2 to about 3.0% by weight solids.
 7. The aqueous sizing composition of claim 6, wherein said aminosilane coupling agent is aminopropyltriethoxysilane, said epoxy silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and said boron containing compound is boric acid.
 8. A glass fiber at least partially coated with a sizing composition comprising: an epoxy resin emulsion containing a liquid epoxy resin having an epoxy equivalent weight of from about 180 to about 210 and at least one surfactant; a silane package including at least one aminosilane coupling agent and at least one epoxy silane coupling agent; a cationic lubricant; a non-ionic lubricant; an antistatic agent; at least one organic acid; and a boron-containing compound.
 9. The glass fiber of claim 8, wherein said aminosilane coupling agent is aminopropyltriethoxysilane, said epoxy silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and said boron containing compound is boric acid.
 10. The glass fiber of claim 8, wherein said at least one surfactant includes: a block copolymer of ethylene oxide and propylene oxide; and a polyoxyethylene-polyoxypropylene block copolymer.
 11. The glass fiber of claim 10, wherein said boron-containing compound is selected from at least one of boric acid, boron oxide, sodium tetraborate, potassium metaborate, potassium tetraborate, ammonium biborate, ammonium tetrafluoroborate, butylammonium tetrafluoroborate, calcium tetrafluoroborate, lithium fluoroborate, potassium tetrafluoroborate, sodium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate and zinc tetrafluoroborate; and wherein said at least one organic acid is selected from the group consisting of acetic acid, formic acid, succinic acid and citric acid.
 12. The glass fiber of claim 8, wherein said epoxy resin emulsion is present in said sizing composition in an amount of from about 60 to about 90% by weight solids, said aminosilane coupling agent is present in said sizing composition in an amount of from about 0.4 to about 0.8% by weight solids, said epoxy silane coupling agent is present in said sizing composition in an amount of from about 10 to about 20% by weight solids, said non-ionic lubricant is present in said sizing composition in an amount of from about 6 to about 10% by weight solids, said cationic lubricant and antistatic agent are present in said sizing composition in an amount of from about 0.4 to about 0.8% by weight solids, said at least one organic acid is present in said sizing composition in an amount of from about 0.4 to about 1.0% by weight solids and said boron-containing compound is present in said sizing composition in an amount of from about 0.2 to about 3.0% by weight solids.
 13. The glass fiber of claim 12, wherein said epoxy equivalent weight is from about 185 to about
 192. 14. A reinforced composite article comprising: a plurality of glass fibers at least partially coated with a sizing composition including: an epoxy resin emulsion containing a liquid epoxy resin having an epoxy equivalent weight of from about 180 to about 210 and at least one surfactant; a silane package including at least one aminosilane coupling agent and at least one epoxy silane coupling agent; a cationic lubricant; a non-ionic lubricant; an antistatic agent; at least one organic acid; and a boron-containing compound.
 15. The reinforced composite article of claim 14, wherein said epoxy has an epoxy equivalent weight of about 185 to about
 192. 16. The reinforced composite article of claim 15, wherein said aminosilane coupling agent is aminopropyltriethoxysilane, said epoxy silane coupling agent is γ-glycidoxypropyltrimethoxysilane, and said boron containing compound is boric acid.
 17. The reinforced composite article of claim 14, wherein said at least one organic acid is selected from the group consisting of acetic acid, formic acid, succinic acid and citric acid.
 18. The reinforced composite article of claim 14, wherein said boron-containing compound is selected from at least one of boric acid, boron oxide, sodium tetraborate, potassium metaborate, potassium tetraborate, ammonium biborate, ammonium tetrafluoroborate, butylammonium tetrafluoroborate, calcium tetrafluoroborate, lithium fluoroborate, potassium tetrafluoroborate, sodium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate and zinc tetrafluoroborate.
 19. The reinforced composite article of claim 14, wherein said epoxy resin emulsion is present in said sizing composition in an amount of from about 60 to about 90% by weight solids, said aminosilane coupling agent is present in said sizing composition in an amount of from about 0.4 to about 0.8% by weight solids, said epoxy silane coupling agent is present in said sizing composition in an amount of from about 10 to about 20% by weight solids, said non-ionic lubricant is present in said sizing composition in an amount of from about 6 to about 10% by weight solids, said cationic lubricant and antistatic agent are present in said sizing composition in an amount of from about 0.4 to about 0.8% by weight solids, said at least one organic acid is present in said sizing composition in an amount of from about 0.4 to about 1.0% by weight solids and said boron-containing compound is present in an amount of from about 0.2 to about 3.0% by weight solids.
 20. The glass fiber of claim 19, wherein said glass fiber is selected from at least one of A-type glass, C-type glass, E-type glass, S-type glass, R-type glass, AR-type glass and E-CR-type glass. 